Banner-waving protester Stuart Holmes briefly hijacked the fourth plinth just minutes before the One & Other art work was officially launched today - and received admiration from the project's creator Antony Gormley.

The anti-smoking campaigner, who declined to give his age, said he did not bother to use a rope and kept fit by cycling.

He refused to move on as Gormley attempted to make a speech about his project and stood defiantly with his banner, which stated: "Save the children. Ban tobacco and actors smoking."

After standing on the plinth for several minutes, Mr Holmes decided to step onto a JCB as Rachel Wardell, the project's first official occupant, took her place.

He said he had heard about the project on the radio and decided to turn up.

Mr Holmes, one of the most dedicated anti-smoking campaigners of the past quarter of a century, said he usually protests outside London's High Court.

He said: "I've stood outside the High Court for 14 weeks.

"Everybody totally ignores this message.

"All you have to do is to ban tobacco and stop actors smoking in films."

He did not believe he had ruined Mrs Wardell's moment, saying: "I don't think I took anything away from her... the biggest threat to children is tobacco addiction... we employ Government to take care of us."

He chatted to a Police Community Support Officer before making his way off.

Mr Holmes, originally from Withington in Manchester, said he was based in London and had been protesting against smoking for 26 years.

He has regularly turned up at party political conferences, invariably standing behind politicians as they were being interviewed for television, brandishing his banners for all to see.

TV presenters were often at a loss to conduct their interviews in places where their exchanges were not distracted by Mr Holmes's brash methods to achieve the greatest possible publicity for his cause.

When it was put to him that this sort of interaction may be what Gormley wanted, Mr Holmes said: "Two birds with one stone, maybe."

Gormley appeared relaxed about the incident, describing Mr Holmes as "an excellent warm-up act if the whole thing is about freedom of speech".

The sculptor said: "He chose his moment very well and I take my hat off to him."